It has been more than a decade since major national legislation passed in August 1996, changing the structure of public assistance programs in the United States. During that time period, researchers from many fields have tried to evaluate the various effects of these changes on the behavior and well-being of low-income families. These changes have been among the most thoroughly evaluated public policies in history. Yet, it is striking how many questions about the effects of this policy change remain unanswered. This paper is designed to summarize the state of this literature, discussing what we know and what we don’t know about the effects of welfare reform. (author abstract)